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PHEVs produce nearly five times greater global warming emissions than lab-reported figures show, according to a new report.

Growing Discrepancy In Lab and Real-World CO2 Output

Statistics shows that PHEVs emit just 19% less CO₂ than traditional petrol and diesel cars, according to analysis carried out by a non-profit organization. This differs sharply with laboratory tests, which assumed a three-quarters reduction in emissions.

Analysts examined data from onboard fuel consumption meters of 800,000 vehicles sold in Europe from 2021 and 2023. They found that actual CO₂ emissions from PHEVs in 2023 were nearly five times greater than lab estimates, up from three and a half times in 2021.

“Actual CO2 output are rising, while lab-reported figures are falling,” stated a lead researcher involved in the study. “This gap is growing and poses a serious issue. Consequently, PHEVs pollute almost as much as gasoline vehicles.”

Primary Factors Behind the Discrepancy

Researchers linked the majority of the gap to inflated estimates of the “utility factor” – the percentage of miles driven in battery mode compared to overall distance. The team found that just a quarter of travel was completed in EV mode, whereas lab assumptions suggested over four-fifths.

Even, when running in electric mode, emission amounts were significantly higher than official estimates. This happened because EV motors were insufficiently powerful enough to function alone, leading to combustion motors burning gasoline for almost a third of the distance completed in electric mode.

Policy and Economic Implications

According to estimates, the underestimation of PHEV CO2 output allowed several major carmaker groups to escape over €5bn in fines from 2021 and 2023, by artificially simplifying adherence with European Union average fleet CO₂ standards.

Additionally, owners of PHEVs could spend about €500 extra per year in operating costs than would be estimated under laboratory tests.

“The bold statements that manufacturers often promote about their plug-in hybrid vehicles are obviously way off the truth,” commented a transport expert. “Consumers are being duped into thinking that by purchasing a PHEV, they are benefiting the environment and saving money. Actually, PHEVs are little improved than regular gas and diesel vehicles in terms of fuel use, CO₂ emissions, and running expenses.”

Policy Debate and Industry Lobbying

Plug-in hybrid cars have lately been brought back into policy debates as carmakers have pressed the EU to relax CO₂ standards. A proposed prohibition on new internal combustion cars in 2035 has faced intense pressure from the car industry and opposition from EU countries with significant automotive industries.

Some senior officials have suggested plug-in hybrids as a possible “flexibility” solution to introduce in the legislation.

One external energy policy specialist, who was not involved with the research, described the report a “very useful addition” after years in which parts of the automotive sector claimed there was too little data to properly assess actual emissions.

“The results show, without question, that the difference between official and actual PHEV fuel consumption and CO₂ emissions is much, much greater than for gasoline or diesel vehicles,” they stated. “All policy changes concerning PHEVs should be made with utmost caution and considering this data.”